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Rosario Pereiro

Publications and source records attributed to Rosario Pereiro.

6 recordsLinked to original sources
PubMed2005

In-depth profile analysis of thin films deposited on non-conducting glasses by radiofrequency glow-discharge-optical emission spectrometry.

The potential of radiofrequency glow-discharge-optical emission spectrometry (rf-GD-OES) for quantification of thin films on non-conducting materials has been investigated. A commercial rf-GD chamber from Jobin Yvon operated at 13.56 MHz with Ar as discharge gas was used. The signal integration time was 0.1 s. The effect on emission yields of thin conducting layers on glasses of different thickness was studied in detail, using the rf-GD in the common operating mode "constant pressure-constant forward power". Calibration curves were obtained for two types of material-conducting reference materials and a set of non-conductors comprising homogeneous glass of known composition and three different thicknesses coated (or not) with thin layers of gold. Qualitative and quantitative in-depth profile analyses of different coated non-conducting samples were investigated. A variety of samples, including different thick glass substrates (from 1.8 to 5.8 mm), different thin films deposited on homogeneous glasses (from 6 nm to 35 nm), and different kinds of coating (conductors such as Fe, Ni, Cr, Al, and Nb and non-conductors such as Si3N4) were studied at 450 Pa pressure and 20 W forward power. The quantitative in-depth profiles proved satisfactory and results for depths and concentrations were similar to nominal values.

Journal Article↗
PubMed2005

Molecularly imprinted polymers based on iodinated monomers for selective room-temperature phosphorescence optosensing of fluoranthene in water.

Aiming at enhancing the advantages of traditional molecularly imprinted polymers (MIPs) for chemical sensing, a new MIP design approach introducing an internal heavy atom in their polymeric structure is described. Based on the heavy-atom effect, the novel polymer allows one to perform room-temperature phosphorescence (RTP) transduction of the analyte. The synergic combination of a tailor-made MIP recognition with a selective RTP detection is a novel concept for optosensing devices which is assessed here for simple and highly selective determination of trace amounts of fluoranthene in water. The noncovalent MIP was synthesized using the laboratory-synthesized tetraiodobisphenol A as one of the polymeric precursors and fluoranthene as template. In the presence of an oxygen scavenger, the iodide included in the polymeric structure induced efficient RTP emission from the analyte, once recognized by the MIP. The developed optosensing system has demonstrated a high specificity for fluoranthene against other polycyclic aromatic hydrocarbons. Detection limit for the target molecule was 35 ng/L (5-mL sample injections), and the linear range extended above 100 microg/L of the analyte. The polymer can be easily regenerated for subsequent sample injections (at least up to 450 cycles) with acetonitrile. The synthesized sensing material showed good stability for at least 6 months after preparation. The feasibility of monitoring fluoranthene in real samples was successfully evaluated through the analysis of five spiked river water samples.

Journal Article↗
PubMed2004

A radiofrequency glow-discharge-time-of-flight mass spectrometer for direct analysis of glasses.

A radiofrequency (rf) glow-discharge (GD) ion source coupled to a commercial on-axis time-of-flight mass spectrometer (TOFMS) has been developed for the direct analysis of non-conducting samples. Different instrumental configurations of the rf-GD source, including the optional use of a sampler cone and the possibility of allowing electrical floating of the discharge, were evaluated first with a conducting sample. Higher ion signals were obtained when the GD was electrically floating and no sampler cone was used. A homogeneous glass was then analyzed using two different rf-GD configurations--with a sampler cone and discarding the use of the sampler cone. The atomic mass spectra obtained with the TOFMS using both configurations were compared. Analyte signals were systematically higher for the latest mode which avoids the sampler cone. The analytical capability of the proposed rf-GD-TOFMS system for the analysis of thick glasses, up to 6 mm, has been investigated in terms of sensitivity, isotopic ratio accuracy, and mass-resolving power. Different homogeneous glasses (including glasses as thick as 6 mm) have been analyzed and major and minor elements were detected. Isotope ratio accuracies of about +/-1% and mass resolving powers of about 700 were observed.

Electromagnetic Fields↗
PubMed2004

Radiofrequency glow-discharge devices for direct solid analysis.

The enormous potential of radiofrequency glow discharges (rf-GD) as photon, atom, or ion sources, coupled to spectrometric techniques, for rapid direct analysis of almost any conductor, semiconductor, or insulating material with good in-depth resolution has been demonstrated world-wide. This outstanding performance has prompted a great effort to develop and characterise rf-GD for direct materials analysis in recent years. The state of the art of rf-GD coupled to atomic absorption spectrometry, optical emission spectrometry, and mass spectrometry for direct solid analysis is reviewed here. A description of the principles of operation of the rf-GD and attempts to model these discharges are also given. Rf-GD instrumentation, both developed at research laboratories and commercially available, is described. Several practical examples are given demonstrating the capabilities of these techniques for bulk and depth-profile analysis. Finally, the research gaps to be filled for full implementation of rf-GD spectrometric techniques in industry and research centres alike for materials science studies and technical development are discussed.

Journal Article↗
PubMed2004

Radio frequency glow discharge-optical emission spectrometry for direct quantitative analysis of glass.

Direct solid quantitative analysis of glass by radio frequency (rf) glow discharge-optical emission spectrometry (GD-OES) by using special silicate glasses of very different composition (e.g., the SiO(2) content varied from 10 to 70%, the CaO content from 0 to 25%, the Na(2)O content from 0 to 15%, the K(2)O content from 0 to 19%, etc.) for calibration is investigated in detail. The effect of sample thickness is studied by using calibration standards and samples of different thickness than that considered as "standard" in our experiments (3 mm). Considering the variable concentrations of easily ionized elements present in the different glass specimens, measurements of the Mg(II) 280.27-nm/Mg(I) 285.21-nm line intensity ratio for the calibration standards and samples containing magnesium were carried out to check the plasma robustness. Results showed that this indicator value remained virtually constant for all the glasses assayed. The proposed quantification scheme is based on the "constant emission yield" concept in which the measured analytical signals were corrected for thickness differences relative to the 3-mm "standard thickness". In addition, better fittings to linear plots were obtained when using discharge Ar emissions as the reference signal. Results for the simultaneous determination of the glass major components (SiO(2), Na(2)O, CaO, MgO, Al(2)O(3), and K(2)O) by rf-GD-OES in two samples of different thickness (3 and 1.1 mm) showed good agreement with the expected results.

Journal Article↗